The present invention relates to a contact image sensor module and an image reading device equipped with the same.
Image reading devices equipped with a contact image sensor module (see Patent Document 1) have been generally known. Since a contact image sensor module is short in the optical path of the optical system, an image reading device can be made compact readily.
However, since a contact image sensor module is shallow in the depth of field, an original that is positioned at a position away from a platen surface of an original platen cannot be read clearly. For example, the image reading device described in Patent Document 1 cannot read a 35 mm film, held in a holder, etc., clearly.
The image reading devices described in Patent Documents 2 and 3 are equipped with a plurality of optical systems and can clearly read reflection originals and transmission originals by the switching of the optical path in accordance with the original. However, the image reading devices described Patent Documents 2 and 3 are complex in the arrangement of the optical system, long in optical path, and thus high in manufacturing cost and not suited for compact size.
Further, a contact image sensor module is equipped with an image sensor of a length that is in accordance with a maximum reading width for an original. Thus with an image reading device with a maximum reading width, for example, of A4 size width, even for increasing the reading resolution for a 35 mm film, the resolution of the image sensor of the A4 size width must be increased. In general, the higher the resolution of an image sensor, the greater the noise generated in the image sensor. Thus with the image reading device described in Patent Document 1, if the resolution of the image sensor is to be increased in accordance with an original that is small in original size but high in the recording density of image information, as in a 35 mm film, the image quality of the read image of an original of comparatively low recording density of image information, as in a printed document, drops for all original sizes.
A contact image sensor module is equipped with an LED that emits light of a red color, an LED that emits light of a green color, and an LED that emits light of a blue color, and performs reading of a color image by lighting up these LED's in a time-divided manner. The image reading device described in Patent Document 1 is thus slow in reading speed.
The image reading devices described in Patent Documents 2 and 3 are equipped with a plurality of optical systems and enable an original to be read at a desired resolution by the switching of the optical path in accordance with the original. However, the image reading devices described Patent Documents 2 and 3 are complex in the arrangement of the optical system, long in optical path, and thus high in manufacturing cost and not suited for compact size.    Patent Document 1: Japanese Unexamined Patent Publication No. 2001-133906    Patent Document 2: Japanese Unexamined Patent Publication No. 2003-37712    Patent Document 3: Japanese Unexamined Patent Publication No. 2003-37713